SANTA ANA, Calif. -- Authorities in Southern California said they believe two of the fires that recently ravaged the area were intentionally started.

Authorities have offered a $150,000 reward for finding the arsonists believed to be responsible for the Rosa fire in Riverside County and the massive Santiago Canyon fire in Orange County, CBS News reported Friday.

Two men have been arrested and one other questioned but authorities wouldn't comment on the suspects.

Officials earlier said the Santiago Canyon Fire had been determined by a task force of federal, state and local agencies to have been started by arsonists in two separate "points of origin."

Orange County Fire Authority Chief Chip Prather said in a news conference that the fire was set in the perfect spot to inflect maximum damage.

"The persons or persons who did this were either exceptionally lucky or they have some knowledge about where you might want to do the most damage when you set a fire," he said.

"I wonder, frankly, if we didn't have this arson caused fire here, how many of our resources we might have had available to respond to other parts of the state."